Yes it did look like outputted binary code. Opera has an advanced algorithm to determine if a connection error has taken place. It relies on content-length header that is transmitted from the server and generated by php forum software. There appears to be a bug within some php builds (or forum codes) that gzips the content okay, but reports the content-length in an incorrect way. Opera trusts this reported length, but errors out when the actual received data doesn't appear to be the same length. Forcing Opera to behave like FF or IE takes out the Opera algorithm for determining connection errors and in the end everything seems to work okay (the content-length sent by the server is being ignored by both IE and FF). I understand there are two fixes for this: 1) detecting if the browser is identified as Opera and just turning off gzipped compression for Opera and 2) updating PHP libraries that may have the content-length bug fixed.